Heat-Exchanger Network Synthesis Involving Organic Rankine Cycle for Waste Heat Recovery

This article aims to present a mathematical model for the synthesis of a heat-exchanger network (HEN) which can be integrated with an organic Rankine cycle (ORC) for the recovery of low-grade waste heat from the heat surplus zone of the background process. An ORC-incorporated stagewise superstructure considering all possible heat-exchange matches between process hot/cold streams and the ORC is first presented. On the basis of this superstructure, the model for synthesizing ORC-integrated HENs is formulated as a mixed-integer nonlinear program (MINLP). A two-step solution procedure is proposed to solve the MINLP model. First, a stand-alone HEN is synthesized to minimize the external utility consumption. An ORC is then incorporated into the HEN with the objective of maximizing the work produced from waste heat (in the heat surplus zone below the process pinch) without increasing the use of a hot utility. A literature example is solved to demonstrate the application of the proposed model for industrial waste heat recovery.